This invention relates to a base station, and more particularly, to a base station capable of access control in wireless communication.
Research and development is being conducted on wireless communication systems that employ orthogonal frequency division multiplexing (OFDM) for the purpose of increasing the speed and capacity of wireless communication. In OFDM, information is transmitted on a plurality of subcarriers that are different from one another in frequency and orthogonal to one another. A transmitter that uses OFDM to send a signal generates data to be sent in the frequency domain, converts the generated data into a time domain signal through inverse fast Fourier transform (IFFT), and sends the converted data as a radio signal. A receiver that uses OFDM to receive a signal obtains the original data by converting the received radio signal of the time domain into a frequency domain signal through fast Fourier transform (FFT).
In orthogonal frequency division multiple access (OFDMA), each subcarrier is assigned to a plurality of terminals and multiple access is implemented by multiplexing through OFDM.
Standards for cellular wireless communication systems that use OFDMA include Long Term Evolution (LTE) and Ultra Mobile Broadband (UMB). In these standards, uplink data transmission and downlink data transmission are separately assigned radio resources in units of a predetermined number of subcarriers for each predetermined time section.
The LTE or UMB standard uses adaptive modulation. In adaptive modulation, several different Modulation and Coding Schemes (MCSs) telling which modulation scheme and what coding rate for error correcting coding are to be used for packet transmission are defined, and one optimum for the channel state is selected out of the defined schemes. Deciding on an MCS is also a function of the base station.
The core network of a cellular wireless communication system is at present divided into a circuit switching network for voice communication and a packet switching network for data communication, which are likely to be integrated into a single packet switching network by introducing Voice over IP (VoIP), where voice signals are turned into IP packets. In the event of integration of separate networks that constitute a core network into one, it needs to be guaranteed that a delay in the transmission of a voice IP packet does not exceed a certain amount in order to ensure a satisfactory communication quality. Future wireless communication systems are also expected to act as a means to deliver various other services than voice communication where the quality of service (QoS) in terms of transmission delay and data transmission rate needs to be guaranteed.